clutch/flywheel questions

[Dread Nought]

I've looked, but can't find too much info on the feasibility of changing a 928s ('86.5) with the twin clutch/flywheel set up to a later model style single clutch/flywheel setup. I'm looking for pros, cons, and ease of modification. All that stuff. Thanks for any help.

[Danglerb]

Early clutch is better, single clutch is easier to adjust, but takes more leg pressure and handles less hp.

Whats your goal in doing it?

[Dread Nought]

Some of the main goals are to simply simplify. That intermediate fly wheel can't truly be resurfaced. The owner was planning to supercharge the thing earlier, so we installed a Spec clutch package/lightened flywheel in the car.

Now he's had a change of heart(and a third kid), and has decided he doesn't need the car. That clutch package is too aggressive for most people to enjoy driving it. So to sell it, putting the stock system back in would be better. If we're going to that trouble, being able to get rid of his fairly worn intermediate flywheel would be a nice bonus. I'm just feeling out if it's a good idea, or bad idea.

[Danglerb]

Putting in a single disc from a different model year makes Porsche buyers no happier than that spec clutch. Market sucks right now to sell, I suggest putting ZERO more money in and selling it with the existing clutch. Fewer potential buyers, but not that much real change in net selling price.

[Dread Nought]

Well, it's interesting to have an outside opinion on THAT part of the situation, but I'm more concerned with the what's involved in making the swap should we decide to go that route.

Everything you stated above may be true and relevant, but I still want to research what would be involved. When I said good idea, bad idea I was referring more to what is involved in doing it. Not the marketability. Any ideas on where I could read about someone who has done this?

Back to your other statements. So what makes the early clutch better? Since the 928 trended towards hp/torque increase with every iteration, why couldn't a late model single clutch handle the load an early model twin clutch can? This is the exact type of thing I'm interested in figuring out. Details please. And thanks for the input.

[Pete R]

The dual clutch has more surface area than the single giving it more holding power. It is also smaller in diameter and has less rotational inertia (hope I called it the right thing). The only reason Porsche ever went to the single disc is because the dealerships couldn't easily set them(dual clutches) up with out chatter. Both clutches adequately handle stock hp. It's just the guys that have significant mods that will look to put the dual clutch back in. Since the single disc is fairly easily converted to dual I imagine the reverse would also be true. (though I admit I have never done it). I have had a machine shop successfully machine an intermediate plate on a couple occasions with no problems at all. You may want to explore that a little more.

[Mrmerlin]

machining, resurfacing any of the clutch parts (IE Pressure Plate or Intermediate plate)will reduce the holding power of the clutch.

[Pete R]

machining, resurfacing any of the clutch parts (IE Pressure Plate or Intermediate plate)will reduce the holding power of the clutch.

you are probably technically right.... but the holding power of the clutch is far superior to stock and even slightly modified hp. So even if it factionally reduces the holding power it doesn't matter. If you go "by the book" it's not recommended but "light" machining works perfectly fine. wouldn't take off a lot of material but a minimal scuff to get off a glaze and irregularities works perfect. I know because I have done it.. a few times, with no noticeable difference from all new parts. Given the cost of a new intermediate plate it's something to consider

[lizard928s]

A few corrections.
Machining the flywheel will not reduce holding power.
Single disc clutches are NON adjustable.

While it is possible to convert an 87+ car to dual disc, it is not (without a lot of machining) possible to convert a LH 2.2 car (84-86 ROW, 85-86 US) to a single disc clutch. The reason is that the single disc flywheel has the 60-2 timing ring machined onto it. Meaning it is not removable. The LH2.2 requires a 100-1 ring for the car to run.

So in other words, forget about it. As well the intermediate plate should be set on the bench with a new disc and locked into place. I personally weld them into plate, Mark Kibort drills and pins them. I also just put a stage III+ into my car, I have no slippage, no chatter, and near stock divability.

[Pete R]

As well the intermediate plate should be set on the bench with a new disc and locked into place.

What exactly do you lock together? I'm assuming the pressure plate and the int plate, not the "floating" inner friction plate. What does that accomplish that the bolts don't? I can see it definitely making the install easier.

[lizard928s]

Pete,

Sorry for the delayed response.

I personally bolt the int plate to a flywheel with a NEW friction disc in between. I then take a shim (.020" iirc) and use a besey clamp to clamp this down near each of the H adjusters. I then weld the H adjusters in place so that they cannot move. This allows JUST enough movement for full disengagement of the primary disc. But prevents the H adjusters from sliding back further.
When they slip back further the clutch drags, and things wear quickly.

I have tested this method in a few cars and it works perfectly every time with no further adjustments required.

HTH

[Mrmerlin]

Colin I should have been more specific in that machining the PP or the I plate will reduce the clamping pressure .
Machining the flywheel should not as long as the whole flywheel surface is machined.

The reduction in clamping pressure will in most cases be not noticeable till the power is increased, but is is however still a consideration,
and the discs will not last as long (or be able to be worn down as far) as uncut part would let them be.